Flexible intermediate bulk containers, commonly referred to as bulk bags, are widely used throughout industry to receive, store, transport and discharge a wide variety of flowable materials. By way of example, bulk bags are commonly used in conjunction with grains and other foodstuffs; fertilizers, herbicides, pesticides, and other agricultural chemicals; raw and prepared minerals and chemicals used as primary materials and intermediate materials in various industrial applications, etc. Over the years bulk bags have been manufactured from a variety of materials and in numerous shapes and sizes.
At the present time, most bulk bags are manufactured from woven polypropylene fabric, and are generally rectangular in cross-sectional configuration. Woven polypropylene fabric has proven to be desirable in the manufacture of bulk bags for a variety of reasons. These include: (1) woven polypropylene material is easily acquired and relatively economical to use; (2) woven polypropylene material has proven to be a relatively high strength, relatively light weight material for the construction of bulk bags; (3) woven polypropylene material is readily adapted to relatively economical manufacturing processes, including conventional sewing procedures utilizing industrial-type sewing machines and various adhesive joining techniques.
Although the use of woven polypropylene material in the construction of bulk bags has generally been found to be highly advantageous relative to the use of other available materials for such purpose, one drawback has consistently characterized the use of woven polypropylene as the preferred material for the construction of bulk bags. Being woven, woven polypropylene has interstices between the polypropylene strands which are used to weave the material. Also, when bulk bags are constructed by a means of sewing operations, interstices are formed by the stitches of the seams comprising the bulk bag. Due to these interstices, certain materials, for example, talc, tend to sift out of bulk bags. For this reason, it has become common practice to utilize liners within the basic bulk bag construction to prevent material contained therein from sifting through the woven polypropylene fabric comprising the bulk bag, and through the sewn seams which are utilized in constructing the bulk bag.
Over the years, bulk bag liners have been manufactured from a variety of materials and have been provided in a variety of configurations. One very popular type comprises a gusseted liner. A gusseted bulk bag liner comprises a pair of opposed, substantially planar panels which are interconnected by a pair of inwardly folded (gusseted) panels which, when extended, combine with the originally flat panels to provide a cross-sectional configuration which is matched to the interior dimensions of the bulk bag with which the liner will be used. However, since gusseted bulk bag liners are generally uniform in cross-sectional configuration along the entire length thereof, the opposite ends of the liner do not fit properly through the inlet chute and outlet spout of the bulk bag. In some instances, the material of the liner so fills the inlet chute and the outlet spout that the receipt of and subsequent discharge of flowable materials into and out of the bulk bag are hampered.
Heretofore, various attempts have been made to provide bulk bag liners having cross-sectional configurations which are matched to those of the bulk bag with which they will be used. For example, U.S. Pat. No. 4,781,472 granted Nov. 1, 1988 to Custom Packaging Systems, Inc. of Manistee, Mich. shows a bulk bag liner which is allegedly matched to the configuration of the bulk bag with which it is used. Notwithstanding this and other attempts to provide bulk bag liners that are matched in cross-sectional configuration to corresponding bulk bags, a need exists for economically providing bulk bag liners which have cross-sectional configurations closely matched to corresponding bulk bags.
The present invention comprises an improved gusseted bulk bag liner and method of manufacture thereof which fulfills the foregoing and other requirements of the bulk bag industry. In accordance with the broader aspects of the invention, a continuous web of gusseted bulk bag liner material comprising opposed planar panels and opposed inwardly folded (gusseted) panels connected by longitudinally extending sidewall folds is advanced along a predetermined path. As the gusseted bulk bag liner material moves along the predetermined path it is engaged by four apparatuses which simultaneously cut and reseal the sidewall folds, thereby forming the gusseted bulk bag liner material into a predetermined cross-sectional configuration which closely matches the cross-sectional configuration of the bulk bag in which the liner will be employed.
More particularly, the particular gusseted bulk bag liner to be formed is characterized by a series of width, length and angular dimensions defining a discharge spout portion, a first transition portion, a main body portion, a second transition portion, and an inlet chute portion of the gusseted bulk bag liner to be formed. Such dimensions comprise a program which is stored in the memory of a central processor unit which is utilized to control the cutting of the gusseted bulk bag liner material as it travels along the predetermined path. The movement of the gusseted bulk bag liner material along the predetermined path is monitored to determine both the speed of movement of the gusseted bulk bag liner material and the amount of material advanced. Four simultaneous cutting and resealing apparatuses are each identified with one of the longitudinally extending sidewall fold lines of the gusseted bulk bag liner material. The cutting and simultaneous resealing apparatuses are moved inwardly and outwardly in accordance with the advance of the material as determined by the stored program. By this means there is formed a preformed gusseted bulk bag liner having the predetermined width, length and angular dimensions which characterize each of the zones of the desired gusseted bulk bag liner.